Often, black-and-white pictures, films or text are colored, in order to make them appear more genuine. Films are simply pictures which are attached to one another. Films originally shot in black-and-white are meanwhile shown in color. To this end, they are colored expensively. Formerly, these pictures were manually dyed individually, i.e, picture-by-picture. For cost reasons, this method of coloring pictures or films is no longer cost-effective.
Nowadays, black-and-white pictures or texts are scanned by means of scanners. The black-and-white pictures are then subsequently available in digital form in the memory of a computer. Digital data is more easily processed. With appropriate programs, color information can be allotted to the digital pictures by means of the computer. This assigning of color information is, however, continued to be effected largely manually, as, from the pictures alone, it cannot be ascertained, which color are to be assigned to the individual objects. There is no color information in the pictures. At best, grey-tones of black-and-white pictures serve as a criterion for the color selection. By the grey-tones one can, for example, determine whether a color is slightly stronger or slightly paler. With the coloring of pictures, colors are to be substantially in conformity with reality.
Often, it is completely unimportant which color is allotted to a picture or text. It is only important that the picture or the text has a colorful appearance. The colors of the optical reality play a secondary role.